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HEAVY OILS  (LUBRICATING OILS)                    359

(0-5-1*5 minute) with 2-3 c.c. of approximately 2N-alcoholic potash: in
presence of nitre-derivatives, a blood-red or violet-red coloration appears.
To identify the a-nitronaphthalene, the following method (Leonard) x is
used : .

A small quantity of the oil is gently heated with zinc dust and dilute
hydrochloric acid with occasional shaking. In this way any a-nitronaphtha-
lene is converted into a-naphthylamine, recognisable by its characteristic
disgusting odour. The acid liquid is separated by means of a separating
funnel, rendered alkaline with soda and extracted with ether, the ethereal
solution being evaporated and the residue taken up in a little alcohol and
treated with a drop of sodium nitrite solution acidified with acetic acid :
the appearance of a yellow coloration changing to crimson indicates the
presence of a-naphthylamine.


* *

Heavy mineral oils have a specific gravity usually between. 0-840 and 0-930,
although occasionally the value 0-960 is attained. They should not contain
any marked quantity of oils distilling below 300 and their flash point should
not be below the specified limit laid down in relation to the purpose for which
they are to be used. Usually this temperature is above, and often greatly
above, 140. Heavy oils are classified into numerous types having the following
characters :

Light oils for engines, gearing, motors and dynamos, viscosity- mostly 13-25
(at 20) and flash point 180-220.

Spindle oil, very fluid, viscosity 3-5-15 (at 20), flash point 160-200.

Oils for compressors and refrigerating machines, still more fluid than the
preceding, viscosity 5-7 (at 20), flash point 140-180; the solidification point
should be below  20.

Automobile oils (cylinder], viscosity varying according to the season from
20 to 85 (at 20), flash point 185-215.

Pale heavy oils for engines and gearing, viscosity 25-45 or raore (a"t 2)
flash point 190-220.

Dark heavy oils for locomotives and railway wagons, viscosity 25-60 (at 20)
and consistency varying with the season.

Cylinder oils for steam engines, boiling point high, very viscous (23-60 at
50), moderately thick, flash point 240-315, or, for some qualities, 350 or
higher. These oils are divided further into low and high pressure cylinder oils.

Another type of heavy oil is that used for electric transformers. This should
not contain water or mineral acids (reaction neutral) and should be non-volatile ;
when heated at 100 for some hours it should not decompose (in particular, it
should not give solid products or become acid) ; it should retain sufficient
fluidity at  15 and should have a high flash point. The following requirements
should be satisfied by such an oil : viscosity at 20, 9-8 (Engler) ; specific gravity,
0-8825 ; flash point (Pensky), 185; volatility, determined by heating the oil
for 5 hours at 100, should not exceed 0-06%, or determined by heating for 2
hours at 170, should not exceed i%.

All the oils indicated above are subdivided into numerous types indicated
by numbers or letters or are sold as special brands.

Oils to be used in the open air or in cold localities should not become turbid
or solidify at a temperature somewhat below the minimum to which they may
be exposed. As a rule American oils solidify at o or a little below, whilst those
from Russia do not solidify above  10 or  20 or even lower.

1 Chem. News, 1893, p. 297.25